Re: [RFC] mt76: fix tx hung regression on MT7630E

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Wed, Jul 31, 2019 at 10:19:58AM +0200, Stanislaw Gruszka wrote:
> On Tue, Jul 30, 2019 at 04:55:31PM +0200, Lorenzo Bianconi wrote:
> > > > > diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c b/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > > > > index 467b28379870..622251faa415 100644
> > > > > --- a/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > > > > +++ b/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > > > > @@ -170,7 +170,7 @@ static int mt76x02_poll_tx(struct napi_struct *napi, int budget)
> > > > >  					       mt76.tx_napi);
> > > > >  	int i;
> > > > >  
> > > > > -	mt76x02_mac_poll_tx_status(dev, false);
> > > > > +	mt76x02_mac_poll_tx_status(dev, true);
> > > > 
> > > > I am not sure if we really need mt76x02_mac_poll_tx_status() here since we run
> > > > it in mt76x02_tx_complete_skb() and in mt76x02_tx_tasklet(). Anyway the only
> > > > difference doing so is we do not run mt76x02_send_tx_status().
> > > 
> > > I thought this is the problem, but it was my mistake during testing.
> > > I tested the above change together with mt76_txq_schedule(dev, txq->ac)
> > > change and get wrong impression it fixes the issue. But above change
> > > alone does not help.
> > > 
> > > I tried to add some locking to avoid parallel execution of mt76x02_poll_tx()
> > > and mt76x02_tx_tasklet(), but it didn't help either. So far only patch
> > > originally posted here make the problem gone.
> > 
> > so, in order to be on the same page, if you comment out mt76x02_mac_poll_tx_status()
> > in mt76x02_poll_tx() the issue will still occur. The only to 'fix' it is to run
> > mt76_txq_schedule_all() in mt76x02_poll_tx(), right?
> 
> Yes.

Err, no, I should read more cerfully. It is partiall revert of 
41634aa8d6db ("mt76: only schedule txqs from the tx tasklet") : 

diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c
index 5397827668b9..fefe0ee52584 100644
--- a/drivers/net/wireless/mediatek/mt76/tx.c
+++ b/drivers/net/wireless/mediatek/mt76/tx.c
@@ -598,7 +598,7 @@ void mt76_wake_tx_queue(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
        if (!test_bit(MT76_STATE_RUNNING, &dev->state))
                return;
 
-       tasklet_schedule(&dev->tx_tasklet);
+       mt76_txq_schedule(dev, txq->ac);
 }
 EXPORT_SYMBOL_GPL(mt76_wake_tx_queue);